22 substance with a unique potential for application in the field of concrete construction. RESEARCH PROGRAM OVERVIEW Results are described from a pilot investigation aimed at evaluating the potential for using soy methyl ester–polystyrene (SME–PS) blends as both an additive and a topical application for concrete. The program examines the influence of SME–PS on the fresh properties, fluid transport properties, and the mechanical properties of concrete. Table 1 is a matrix of the testing program that was used in this inves- tigation for examining SME–PS blends in both topical and admixed applications. BACKGROUND ON SME–PS BLENDS Oil crops, such as soybeans, are used mainly for livestock feed (8). The extracted oils from this feed have many potential uses (soaps, lubricants, crayons, candles, etc.) including the production of SMEs through transesterification. SMEs are biodegradable, nontoxic, renew- able materials with potential application in the construction industry. Specifically SMEs are hydrophobic and have the potential to repel water or reduce fluid transport if used in concrete (9). The addi- tion of SMEs leads to the modification of concrete properties while also creating a “green” concrete due to their biodegradable and nontoxic form. SMEs consist of plant oils that are composed of long-chain fatty acids (14 to 20 carbons), which are esterified to a methyl group. Methyl esters are produced from plant triacylglycerides (oil) by alkaline-catalyzed transesterification with methanol. Each molecule of triacylglyceride reacted requires three molecules of methanol, resulting in the production of three molecules of methyl esters and one molecule of glycerin. While remaining biodegradable and nontoxic, methyl esters have physical properties that are distinctly different from those of the triacylglyceride (soybean oil) since SMEs are excellent solvents for many synthetic polymers, unlike the original oil, which is a poor solvent for these materials. Since the SME is an excellent solvent, polystyrene (PS) and polyvinyl chloride (PVC) can be dissolved in the SME to make an SME–polymer combination that creates blends with significantly different fluid properties; this procedure enables the selection of blends best suited for certain applications. Further- more, the addition of PS can lead to its deposition in the pores of the concrete. An effort was made in this pilot study to quantify the effect Can Soy Methyl Esters Reduce Fluid Transport and Improve Durability of Concrete? Kevin C. Coates, Samia Mohtar, Bernard Tao, and Jason Weiss a ab b a a b a a a a a a ab a a a aa a b a a a a a a b ( )a a a a a a b a a a a a a a ab a b ba ab a a a a a a a b aa a a a a a a Nearly all problems that lead to the deterioration of concrete can be related to the presence of moisture or transport of fluid in the pore structure of the concrete (1). Common forms of this type of deterioration would include chloride ion ingress and freeze–thaw damage. Many methods have been used in the past to reduce the ingress of fluid to preserve the durability of concrete. These meth- ods include improved mixture proportioning (2), special curing techniques (3), and the use of membrane coatings, penetrating sealers, and crack sealants (4 ). For example, the use of linseed oil in certain forms has shown that hydrophobic solutions can be used as penetrating sealers on pavements to reduce the absorp- tion of moisture (5). The research program discussed here evalu- ated the potential for using soy methyl esters (SMEs) for similar purposes. This research program is similar conceptually to classic studies dealing with substances such as linseed oil (6 ); however, SMEs are a derivative of soybean oil (as opposed to flax oil), which has a different chemical composition and structure after esterification, consequently properties that differ from those of the original oil. These properties include high solvent capacity, altered surface ten- sions, and enhanced viscosities. All of these properties lead to a K. C. Coates and J. Weiss, School of Civil Engineering, 550 Stadium Mall Drive, and S. Mohtar and B. Tao, Department of Agricultural and Biological Engineer- ing, 225 South University Street, Purdue University, West Lafayette, IN 47907. Corresponding author: K. C. Coates, [email protected]. Transportation Research Record: Journal of the Transportation Research Board, No. 2113, Transportation Research Board of the National Academies, Washington, D.C., 2009, pp. 22–30. DOI: 10.3141/2113-03
Can Soy Methyl Esters Reduce Fluid Transport and Improve Durability of Concrete?
May 06, 2023
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